Climb Milling any implications

Hi Guys,

i am currently going through what I know or think I know with regard to using my Sherline mill to make a pinion cutter. I have found several factors that could have added minor errors such as using the mill ends inappropriately in terms of depth cut etc. However I have come across climb milling v conventional milling. It appears at first glance to be just the direction you move the end mill towards the stock.

Can anyone give a good simple explanation as to what I should know about climb milling and any likely implications when using the Sherline Mill.

I have no idea about how naive this question is so charity may be needed.

Regards

Chris

Hello Chris, not a naive question at all. The main problem would be the tendency of the cutter dragging the work in unless your mill is fitted with backlash eliminators.

Climb milling usually results in a better finish.

Brian

hi Chris if you climb mill on a conventional mill it will drag the work into the cutter depending how much backlash you have in the leadscrews upcutting will push the work away .it is recommend to upcut on conventional mills.

Geoff

With climb milling the cutting force pulls the work through the backlash and suddenly increases the depth of cut. On your mill I would suggest you don't even try, especially cutting pinions.

It's easy to find on the web

web

Yes all the above. I have been down this road myself. Got help on here & avoid climb milling like the Plaque now. I have seen it used to just finish a part to get a smooth finish, by only taking a very light pass.

I was using a 2 flute 10mm when it dragged the cutter out of the collet & ruined the job & the end of the cutter.

Needless to say the machine stopped pretty quick too.

Steve.

In the apprentice workshop I was tought never to climb except on materials that work hardened. I have remained faithful to that teaching.

During a previous discussion, on this forum, about climb milling I ask a couple of friends who had worked in tool rooms whether they had climb milled. The reply, in both cases, was never.

I think you would need a large and very rigid machine to climb mill anything.

JA

The simplest and most basic advice is to climb mill only on very light cuts or spring cuts after doing all the main metal removal cuts feeding against rotation direction.

The risk in climb milling is that, if the table/leadscrew combination has significant backlash, taken out during approach against the direction of movement, that a leading flute of a climb-milling cutter will pull the table in the same direction to take up the backlash the opposite way, potentially presenting the next flute with a slice to cut that is of full depth of cut and as thick as the portion of the backlash that has been taken up. The stress might be more than the cutter can stand - bang.

I once broke a nice 8mm carbide endmill I'd been using for years by a moment of carelessness like this. Everybody makes mistakes - just try to minimise them.

A conventional feedscrew will almost certainly have some backlash and acquire more with wear, attempts to control backlash can be mechanical or hydraulic, a recirculating ball feedscrew and nut is a successful way to minimise backlash. Because the finish when climb milling is usually better than conventional I will risk a very light final cut with the axis locks used to add some extra drag, this is a risk and getting it wrong can trash the job and break the cutter. Developing some feel for the machine will give a better chance of success but as this will be a finishing cut you could spoil some hours of work in a moment. I have seen a powerful mill haul the job out of an 8” vice and put gashes all along the job, not with me driving though.

Mike

Plenty of clear descriptions on this page but the cnccookbooks has it the wrong way round in their picture, so beware.

**LINK**

Emgee

I currently use an Emco F1 cnc mill equipped with ballscrews on all axis and always use climb milling so small mills can climb mill without the problems sometimes experienced.
Link below shows climb milling 6082T6 aluminium with a 12mm 4f HSS endmill

Emgee

https://youtu.be/udDhZlu53e0

Edited By Emgee on 23/09/2020 15:23:37

Machine rigidity has more effect on climb milling than feedscrew backlash. Machine rigidity in this case includes play in the quill and bearings, poor gib adjustment flexing in the cutter mounting and in the job itself. There is no little warning of trouble when climb milling, it has an almost instantaneous onset!

Even on a very small milling machine climb milling with a very small cutter (say less than 3mm) is going to be a painless operation unless the slides are very loose.

I climb mill 80% of the time in non ferrous and plastics using cutters up 16mm on an Emco Mentor. I have the gib adjustment set to what feels right to me but certainly not overtight.

Ian P

I will climb mill on my little CNC (Novamill) with no problem as it has ballscrews and is very rigid.

On the bigger VMB I only climb mill when finishing ali with the side of a cutter - take the last main cut normally then wind back without moving the cutter or maybe just adding 0.1 mm more. This gives a much better finish and so far hasn't resulted in grief.

On steel on Chris' little mill especially making pinions I wouldn't even try.

Sherline state conventional milling should be used for all hard materials and roughing but that for lighter finishing Climb milling can be used. I am still getting my head round all the permutations. OK I get that you can face stock moving it say left or right but what about end on on the Y axis if I were to mount the stock as in the diagram and feed as per arrow this is climb milling and a no no position then??

Chris

Edited By Chris TickTock on 23/09/2020 18:09:04

Chris climb and conventional really only applies when using one side of the cutter upto about 1/3rd of its diameter.

In your sketch if looking down the spindle then the part of the tool between 9 and 12 o'clock is conventional and from 12 to 3 o'clock is climb and the two forces will cancel each other out so no real risk of the work being drawn into the cutter. In fact the area from 11 to 1 o'clock will have little effect in the Y axis but if a very deep cut were taken there is a chance the tool could flex to the left.

Edited By JasonB on 23/09/2020 18:35:37

Thanks Jason, will leave it as tired and have a look tomorrow with a fresh mind.

Chris

Jason, OK I think I get most of this now, my error was not understanding that cutter direction matters only in relation to where it is milling on the stock (silly idiot).

Having said all that are there rule of thumbs for positioning the cutter on a certain side and moving the stock in a given direction?

Such as for taking a face cut off with cutter in front of stock at left front corner move stock to left for conventional milling?

Chris

.

Chris,

Just consider your own sketch, and what would happen if you decide to widen that slot by shifting left or right on the X axis.

Thinking it through is usually better than learning ‘rules of thumb’ by rote.

MichaelG.

Chris, the first hit on dave's web search gives a good image of cutter in relation to each sid eof work for external cutting.

This would be a typical setup to square off the end of a piece of stock using conventional cuts